This Program Project on Thrombosis and Plasma Proteins has as its goal the development of a coordinated effort by independent investigators aimed at: 1) identifying factors and defining the principles of (in vitro, in situ, in vivo) operation of normal coagulolytic machinery, 2) study of foreign-protein interactions which would modify normal functions of the coagulolytic machinery as exemplified by the streptokinase-plasminogen interaction, and the endotoxin-serum-membrane interaction and 3) employing assays of coagulolysis and other analytic tools together with models of their functions as probes in a systematic study of the mechanism of pertrubation of coagulolytic proteins and systems by foreign particles (SK, endotoxin), and in detecting and defining the causes of a variety of hypercoagulable states. Techniques ranging from those used in protein chemistry, physical chemistry, ultrastructural anatomy and physiology and including clinical medicine and biology will be coordinated in an extensively conceptualized study of certain aspects of the thrombotic process and its abnormal function.